The usage of a boom carried by a vehicle may occur in different domains. For example, in the agricultural domain, a tractor carrying a boom may be used to spray a liquid or a gas (e.g. water, fertilizer, insecticide) in a field. FIG. 1 illustrates such a boom 10, having two sections 12 and 16 extending on each side of a tractor 20 to cover a large area; each section 12 and 16 being capable of spraying the liquid or the gaz. The boom 10 may be directly carried by the tractor 20. Alternatively, as illustrated in FIG. 1, the boom 10 may be carried by a towed vehicle 30 attached to the tractor 20. The towed vehicle 30 supports a tank containing the liquid or the gas to be spread by the boom 10.
The boom is generally not rigidly fixed to the carrying vehicle, but may move rotationally around a longitudinal axis, located at a center of the boom and perpendicular to the length of the boom. Thus, when the carrying vehicle is driving on an inclined ground or on a generally plane ground with random irregularities, the rotational movement of the boom may contribute to maintain a global balance of the carrying vehicle and the boom. A rigidly fixed boom may lead to a partial overturn of the carrying vehicle or may cause damages to the boom; while a rotationally fixed boom contributes to attenuating the impact of the profile of the ground on the stability of the carrying vehicle and the boom. The global balance of the carrying vehicle and the boom is affected, because the orientation of the boom with respect to the ground is directed by gravity, while the orientation of the carrying vehicle with respect to the ground is directed by the profile of the ground.
Additionally, each section of the boom may be independently moved vertically (adjustment of the height of a section with respect to the ground) or extended horizontally, in order to adapt to specific conditions of use or to a specific profile of the ground. Such a vertical movement of one of the sections may modify the global balance of the boom, and trigger a rotation of the boom around its axis.
An optimal configuration for operating the boom is when the boom and the carrying vehicle have the same orientation, namely when they are both horizontally aligned with the ground. FIG. 2A illustrates the optimal configuration, where the boom 10 and the carrying vehicle 20 are both horizontally aligned with the ground 50. FIG. 2B illustrates another case, where the optimal configuration is maintained, although the ground 50 is not horizontal. FIG. 3 illustrates a non-optimal configuration, where the boom 10 is not horizontally aligned with the ground 50. In this case, the inclination of the boom 10 shall be corrected, to obtain the optimal configuration illustrated in FIG. 2A.
However, in specific circumstances, the configuration illustrated in FIG. 3 shall be maintained for a certain amount of time, before reverting to the optimal configuration of FIG. 2A. For example, the vertical movement of one of the sections 12 or 16 of the boom 10 may lead to the non-optimal configuration of FIG. 3. Specifically, the difference of height between the two sections 12 and 16 modifies the global balance of the boom 10 and triggers a rotation of the boom 10 around its axis, leading to the non-optimal configuration of FIG. 3. However, trying to correct the inclination of the boom 10 during the vertical movement of the section 12 or 16 may lead to a series of uncontrollable actions/reactions. Therefore, it is more efficient (and eventually safer) not to act on the inclination of the boom 10 during the vertical movement of the section 12 or 16, and to correct the non-optimal inclination afterwards.
There is therefore a need for a method and system for controlling an inclination of a boom with respect to a vehicle carrying the boom.